% swapbytes reverses byte ordering converting little-endian big-endian
%*************************************************************************************
%
% MATLAB (R) is a trademark of The Mathworks (R) Corporation
%
% Function: swapbytes
% Filename: swapbytes.c
% Programmer: James Tursa
% Version: 1.1
% Date: August 4, 2009
% Copyright: (c) 2009 by James Tursa, All Rights Reserved
%
% This code uses the BSD License:
%
% Redistribution and use in source and binary forms, with or without
% modification, are permitted provided that the following conditions are
% met:
%
% * Redistributions of source code must retain the above copyright
% notice, this list of conditions and the following disclaimer.
% * Redistributions in binary form must reproduce the above copyright
% notice, this list of conditions and the following disclaimer in
% the documentation and/or other materials provided with the distribution
%
% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
% POSSIBILITY OF SUCH DAMAGE.
%
% swapbytes is a mex function that mimics the MATLAB intrinsic function of
% the same name. Mainly intended for those users with older version of MATLAB
% that do not have this intrinsic function available. But there are extensions
% listed below.
%
% Building:
%
% swapbytes requires that a mex routine be built (one time only). This
% process is typically self-building the first time you call the function
% as long as you have the files swapbytes.m and swapbytes.c in the same
% directory somewhere on the MATLAB path. If you need to manually build
% the mex function, here are the commands:
%
% >> mex -setup
% (then follow instructions to select a C / C++ compiler of your choice)
% >> mex swapbytes.c
%
% If you have an older version of MATLAB, you may need to use this command:
%
% >> mex -DDEFINEMWSIZE swapbytes.c
%
% Calling sequence: out1 = swapbytes(in1)
% [out1,out2] = swapbytes(in1,in2)
% etc. (any number of input/output pairs)
%
% Description (from the MATLAB documentation):
%
% Y = swapbytes(X) reverses the byte ordering of each element in array X,
% converting little-endian values to big-endian (and vice versa).
%
% Example 1
%
% Reverse the byte order for a scalar 32-bit value, changing hexadecimal
% 12345678 to 78563412:
%
% >> A = uint32(hex2dec('12345678'));
% >> B = dec2hex(swapbytes(A))
% B =
% 78563412
%
% Example 2
%
% Reverse the byte order for each element of a 1-by-4 matrix:
%
% >> X = uint16([0 1 128 65535])
% X =
% 0 1 128 65535
% >> Y = swapbytes(X)
% Y =
% 0 256 32768 65535
%
% Examining the output in hexadecimal notation shows the byte swapping:
%
% >> format hex
% >> X, Y
% X =
% 0000 0001 0080 ffff
% Y =
% 0000 0100 8000 ffff
%
% Example 3
%
% Create a three-dimensional array A of 16-bit integers and then swap the
% bytes of each element:
%
% >> format hex
% >> A = uint16(magic(3) * 150);
% >> A(:,:,2) = A * 40;
% >> A
% A(:,:,1) =
% 04b0 0096 0384
% 01c2 02ee 041a
% 0258 0546 012c
% A(:,:,2) =
% bb80 1770 8ca0
% 4650 7530 a410
% 5dc0 d2f0 2ee0
%
% >> swapbytes(A)
% ans(:,:,1) =
% b004 9600 8403
% c201 ee02 1a04
% 5802 4605 2c01
% ans(:,:,2) =
% 80bb 7017 a08c
% 5046 3075 10a4
% c05d f0d2 e02e
%
% Extensions of this mex function to the MATLAB intrinsic:
%
% For structures and cell arrays, each component or cell is individually
% converted. Other classes (e.g., vpa, function handles, etc.) are not
% converted; a deep copy is returned instead. swapbytes takes any number
% of input arguments; there must be the same number of matching output
% arguments. Also, swapbytes will convert the complex portion of variables
% as well as the real portion. swapbytes also works with sparse matrices.
%
% For users with later versions of MATLAB, this mex file will clash with
% the actual intrinsic of the same name. If you want to use this mex file
% and still have access to the MATLAB intrinsic, simply rename this file
% and the help file to something unique, like swapbytesx.c and swapbytesx.m
%
% ***************************************************************************/
function varargout = swapbytes(varargin)
disp(' ');
disp('You must build the mex routine before you can use swapbytes.');
disp('Attempting to do so now ...');
disp(' ');
mname = mfilename('fullpath');
cname = [mname '.c'];
if( isempty(dir(cname)) )
disp('Cannot find the file swapbytes.c in the same directory as the');
disp('file swapbytes.m. Please ensure that they are in the same');
disp('directory and try again. The following file was not found:');
disp(' ');
disp(cname);
disp(' ');
error('Unable to compile swapbytes.c');
else
disp(['Found file swapbytes.c in ' cname]);
disp(' ');
disp('Now attempting to compile ...');
disp('(If prompted, please press the Enter key and then select any C/C++');
disp('compiler that is available, such as lcc. Note: Older versons of)');
disp('MATLAB may get lots of errors at this step ... ignore for now.)');
disp(' ');
disp(['mex(''' cname ''')']);
disp(' ');
try
mex(cname);
disp('mex swapbytes.c build completed ... you may now use swapbytes.');
disp(' ');
catch
disp(' ');
disp('Well, *that* didn''t work ... now trying it with mwSize defined ...');
disp(' ');
try
disp(' ');
disp(['mex(''-DDEFINEMWSIZE'',''' cname ''')']);
disp(' ');
mex('-DDEFINEMWSIZE',cname);
disp('mex swapbytes.c build completed ... you may now use swapbytes.');
disp(' ');
catch
disp('Hmmm ... That didn''t work either.');
disp(' ');
disp('The mex command failed. This may be because you have already run');
disp('mex -setup and selected a non-C compiler, such as Fortran. If this');
disp('is the case, then rerun mex -setup and select a C/C++ compiler.');
disp(' ');
error('Unable to compile swapbytes.c');
end
end
[varargout{1:nargout}] = swapbytes(varargin{:});
end
end
